Struct PageAllocator 

pub struct PageAllocator { /* private fields */ }

Hands out page numbers during a save.

Lifetime: one allocator per save_database call. Not thread-safe; not shared across saves.

Implementations

impl PageAllocator

pub fn new(freelist: VecDeque<u32>, next_extend: u32) -> Self

freelist carries the pages from the previously-persisted freelist (sorted ascending by the caller). next_extend is typically 1 for a brand-new save.

pub fn set_preferred(&mut self, pool: Vec<u32>)

Seeds the per-table preferred pool. Drained on subsequent [allocate] calls before any other source.

pub fn finish_preferred(&mut self)

Empties the per-table preferred pool, returning any leftover pages to the global freelist (they’re now free again).

pub fn allocate(&mut self) -> u32

Returns the next page to write. Picks from preferred → freelist → extend. Records the result in used and bumps next_extend if the page came from one of the pools and was past the current high water.

pub fn add_to_freelist(&mut self, pages: impl IntoIterator<Item = u32>)

Adds pages to the global freelist. Used to drop pages that the caller traversed but didn’t end up restaging (e.g., a dropped table’s leaves; the previous freelist’s trunk pages).

Bumps next_extend past any added page so the final page_count covers freelist trunks even if they live past the highest used payload page.

pub fn high_water(&self) -> u32

Page-count to publish in the new header. Equal to 1 + max page handed out after staging.

pub fn used(&self) -> &HashSet<u32>

Every page handed out this save.

pub fn drain_freelist(&mut self) -> Vec<u32>

Snapshot of pages still on the global freelist (i.e., free pages that need to be persisted into trunk pages). Sorted ascending so the encoded freelist trunks are deterministic.